Asthma remains a significant and costly public health problem. In the United States, more than 22 million people have the disease; worldwide, the World Health Organization estimates the population with asthma may be 300 million, and predicts that it will rise to 400 million by 2025.
Despite the development of new medications, rates of hospitalizations and emergency room visits have not declined. Each year in the United States the disease causes approximately 2 million emergency department visits, 500,000 hospitalizations, and 5,000 deaths. In addition, asthma is responsible for an estimated 15 million missed days of school, and 12 million days of work. Total annual costs to US health insurers and employers are greater than $18 billion.
The majority of these exacerbations could be prevented with currently available treatments, however, only 1 in 5 asthmatics has the disease under control. Newly revised national guidelines urge doctors to more closely monitor whether treatment is controlling everyday symptoms and improving quality of life. Physicians, however, have few available tools to assess how well their patients are doing day-to-day. An increasing number of physicians have begun to use periodic, written questionnaires (such as the Asthma Control Test) to monitor patients and determine their level of control. These instruments require patients to accurately recall and report the frequency of symptoms, inhaler usage, and activity level and restriction over some period of time (usually two to four weeks). As a result, these questionnaires are subject to error introduced by biases (recall), different interpretations of symptoms, and behaviors (non-adherence), and only provide information at the time they are used.
Nearly all persons with asthma carry an inhaled medication to immediately relieve symptoms wherever they occur. The frequency with which patients use these medications is one of the most important indicators of how well their disease is controlled. Physicians who could remotely monitor the use of these medications by patients in real-time would be able to identify and help patients in need of additional attention before they suffer an exacerbation.
Asthma is unique in that important medication(s) are often used at the location and time of exposures that cause exacerbations. Many exacerbations are caused by exposure to environmental factors such as allergens, air pollutants, tobacco smoke, and occupational chemicals, but identifying causative exposures or locations that pose a particular threat has been a struggle for public health experts.
Since established risk factors do not explain the prevalence of asthma or its trends over time, it is likely that there are unknown environmental factors that trigger symptoms or contribute to the development of asthma.
Public health officials have been limited to the retrospective analysis of the small proportion of attacks that led to emergency room visits and hospitalizations (the most severe exacerbations). These events indicate where the patient lives or the location of the health facility where they received treatment, but provide no information about where their exacerbation began. Last year, the US Centers for Disease Control and Prevention recommended that the timeliness and geographic specificity of asthma surveillance data be improved.
As a result, real-time tracking and mapping of the locations where persons with asthma use their inhaled medications would improve scientific assessment and management of asthma, and enable better public health surveillance of asthma and its relationship to environmental exposures. Studies of epidemic asthma have demonstrated that understanding the locations where asthma exacerbations occur can help identify important new exposures.
In addition, many patients with asthma triggered by exposures at school or work do not recognize the relationship between their symptoms and specific locations, resulting in missed opportunities to avoid or mitigate the exposure and thereby prevent further exacerbations.
At present, there are no commercially available devices that allow the location where an inhaler is used to be objectively obtained. In addition, there are no commercially available devices that allow physicians to monitor the medication use of their patients in real time, to gauge their control over the disease, and to use technology to determine who needs additional attention. Furthermore, there are no systems that allow public health officials to collect and analyze data on the medication use of individual patients in order to monitor in real time the overall burden of the disease in the community or to guide public health interventions and epidemiological research.
Various systems have been proposed to record the time and date of usage of metered dose inhalers. Two models are currently available in the U.S. market. One device, described in U.S. Pat. No. 5,505,192, attaches to the end of a metered dose inhaler and records the time and date of inhaler use over a 30 day time period. Another device, described in U.S. Pat. No. 6,202,642, captures the time and date of inhaler use, and provides a means to transmit this information at a later time to the health care provider. To accomplish this, the patient must connect their device to a computer.
Several devices that provide means for the two-way transmission of information between a medication and a remote network using wireless technologies have also been proposed. U.S. Pat. No. 6,958,691 describes an inhaler having an electronic data management and display system and a communicator for wireless communication with a network computer system. US application 2006/0089545 proposes use of a cellular phone to transmit information about medication, and to present medication information and treatment instructions to the patient.
The primary aim of both of these devices is to encourage and improve patient compliance with their prescribed medication regimen. As a result, these systems focus on providing education (treatment instructions), monitoring, and supervision. In addition, the above devices provide for two-way communication between the inhaler (or device) and the physician or health care provider, and some allow for controlling or modifying the medication delivered by the inhaler (see U.S. Pat. No. 5,477,849).
Various methods for the epidemiological analysis of medical data and information (such as emergency room visits or hospitalizations, or over the counter medication purchases) have been proposed. However, these systems are focused on establishing a diagnosis or on tracking and analyzing the geographic location(s) of health care utilization (such as emergency room visits or hospitalizations) or the residence of the person with the disease of interest. No known system describes the analysis of the location where the medication is used, or proposes a system for aggregating and making use of information from a population of individuals.